Switching power supply apparatuses have been widely used as power supply units of appliances for common household use, such as home electrical products. A switching power supply apparatus includes a semiconductor device which regulates (for example, stabilizes) output voltage at a constant level through switching operation using semiconductor elements (switching elements such as transistors), for purposes such as improvement of power efficiency by reducing power consumption.
For example, Patent Literature (PTL) 1 discloses a switching power supply apparatus which includes a transformer with a plurality of secondary windings. The switching power supply apparatus disclosed in PTL 1 further includes an average value calculating unit and a voltage feedback control unit.
The average value calculating unit calculates an average value of output voltages generated by the secondary windings. The voltage feedback control unit performs pulse width modulation (PWM) control or pulse frequency modulation (PFM) control to control conduction of a primary winding of the transformer so that the error between the average value calculated by the average value calculating unit and a target setting voltage is zero. The PWM and PFM controls are examples of switching operation of the switching element.